Field of the Invention
The present invention generally relates to devices and methods useful for clot retrieval, and removal devices to treat, among other things, ischemic stroke.
Description of the Prior Art
Currently, the FDA-approved treatment options for an acute ischemic stroke include intravenous (IV) delivery of clot dissolving medicine and mechanical thrombectomy.
For treatment use, clot dissolving medicine, such as the thrombolytic agent (Tissue Plasminogen Activator (t-PA)), is injected into the vasculature to dissolve blood clots that are blocking blood flow to the neurovasculature. Intravenous t-PA is currently limited in use because it must be used within a three-hour window from the onset of a stroke and can result in an increased risk of bleeding. This standard of care leaves room for upgrade, and is only the appropriate approach to treatment for a limited class of individuals, groups and temporally-limited exigent cases.
A second option includes the use of mechanical thrombectomy devices. Such devices are designed to physically capture an embolus or clot, and to remove it from the blocked vessel, thereby restoring blood flow. The major advantage of the mechanical thrombectomy device is it can expand the treatment window from three hours to over ten hours.
Some existing mechanical thrombectomy devices used for increasing blood flow through an obstructed blood vessel include: 1) a filter trap designed and built to collect and remove emboli; 2) a cork-screw guidewire-like device to retrieve embolus; and 3) a stent-like device connected to a delivery wire to retrieve embolus. All of these devices suffer from certain disadvantages.
First, filter-type thrombectomy devices tend to be cumbersome and difficult to deliver and deploy, and a larger-profile guide catheter may be needed to fully remove the embolus. In addition, it is difficult to coordinate precise and predictable movement to position the device properly in the vessel. The device can drift within the vessel, twist, or not be adequately conforming to the vessel wall and, therefore not effective for removing embolus.
Cork-screw guidewire devices can only capture and remove emboli that are firm, or subject to certain mechanical variables such as being held together by itself as one piece. Cork-screw guidewire devices are not effective in removing particulate matter that may be scattered or broken up.
Stent-like mechanical thrombectomy devices are not capable of capturing small emboli that break off from a large embolus (if any), and can lead to complications such as the blockage of distal smaller vessels, vessel dissection, perforation, and hemorrhage arising as a result of over-manipulation in the vessel.
The disadvantages common to all of the devices described above include, for example: 1) the device may capture an embolus, but then lose grasp of it and migrate/deposit it incidentally into another area of the neurovasculature, creating the potential for a new stroke in a different part of the neurovasculature; 2) the device is not capable of capturing small embolus breaking off from the larger embolus and preventing it from migrating to a more distal area of the neurovasculature; 3) the relative large device profile prevents these devices from treating the distal smaller diameter vessels; and 4) risk of sICH (symptomatic Intra-cerebral Hemorrhage) after intra-arterial clot removal in acute stroke patients.
Other flaws in the current mechanical thrombectomy designs include poor visibility/radiopacity, lack of variation in the delivery portion to enhance and improve deliverability, and lack of coatings or modified surface textures on the treatment portion to enhance embolus affinity, etc. In conclusion, there is a great need for improved devices, systems, and methods for restoring blood flow through a blood vessel. None of the existing medical mechanical thrombectomy devices address all necessary needs to date.